Q 26P Show that the (S,S) enantiomer o... [FREE SOLUTION]

Chapter 7: Q 26P (page 367)

Show that the (S,S) enantiomer of this (R,R) diastereomer of 1-bromo-1,2-diphenylpropane also undergoes E2 elimination to give the cis diastereomer of the product. (We do not expect these achiral reagents to distinguish between enantiomers.)

Short Answer

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(S,S)-1-bromo-1,2-diphenylpropane

Step by step solution

Step by step solution: Step 1:E2 elimination

E2 elimination is a one-step mechanism, and carbon-hydrogen and carbon-halogen bonds mostly break off to form a new double bond. Base used in this reaction has huge influence on the mechanism and reaction rate depends on both the substrate and the base involved. The beta-hydrogen and leaving group halogen must be anti-coplanar with each other. Base abstracts the beta hydrogen and simultaneously leaving group gets eliminated and double bond gets formed.

Step-2. Formation of the product

(S,S)-1-bromo-1,2-diphenylpropane undergoes E2 elimination reaction to produce cis-alkene. On converting the Fischer projection of the reactant into wedged-dashed form, we get hydrogen and leaving group, i.e., bromine anti-coplanar to each other which is the required condition for E2 elimination. Then, base abstracts the beta-hydrogen and simultaneously leaving group gets eliminated, which leads to formation of double bond. In product, both the phenyl groups are on same side of double bond, thus, it is a cis product.